Botulinum toxin type A, popularly known by one of its tradenames, Botox, is a protein and neurotoxin that is used in various cosmetic and medical procedures. In cosmetic applications, a botulinum toxin injection may be used to prevent the development of wrinkles by paralyzing facial muscles. In non-cosmetic applications, botulinum toxin may be used to treat conditions of excessive and inappropriate muscle contraction, spasticity (persistent states of muscle contraction), sphincter contraction, eye-movement disorders, tics and tremors.
Before the botulinum toxin can be administered to a patient by means of an injection, a clinician must reconstitute the botulinum toxin supplied by the manufacturer with a diluent, typically a saline solution. The botulinum toxin is normally supplied by the manufacturer in a vial containing a certain number of ‘units’, e.g. 50 units or 100 units, which vial comes with an instruction to dilute it with a certain volume of diluent, e.g. 1.25, 2.0, 2.5 or 5.0 ml. For instance, in case a 50-unit vial is to be diluted with 1.25 ml of saline solution, the resulting mixture comprises 4 units per 0.1 ml. When the same 50-unit vial is diluted with 2.0 ml or 2.5 ml of saline solution, the resulting mixture comprises 2.5 units per 0.1 ml and 2 units per 0.1 ml, respectively. The prescribed mixture ratio may vary with each manufacturer, and the treatment to be carried out with the final solution.
Importantly, a treatment with botulinum toxin may typically be defined in terms of a number of units, e.g. 1-5 units, to be injected across various sites of a body region to be treated. A chronic migraine treatment may, for example, prescribe that 5-unit injections are to be administered across seven different head/neck muscles.